Any quest to lose weight involves monitoring both calories in and calories out, as the key to dropping unwanted pounds is expending more calories than you consume.

Yet time and time again researchers have revealed that most people underestimate the number of calories they put in their mouth and overestimate the amount of energy they expend.

How far off are their estimates? A research team out of the University of Ottawa put a small group of study subjects on a treadmill where they walked briskly until told their workout was over. Then after a quick shower, they were led to a buffet and asked to eat what they considered the caloric equivalent of their workout.

Unaware of how much energy they expended, the study subjects estimated they burned off three to four times more than the 200 to 300 calories they burned. And while they ate less than their estimated calorie burn, they consumed two to three fold more calories than needed to match the number they expended in the gym.

Similar miscalculations occur daily all over the world as people try to drop unwanted pounds and maintain a healthy weight through diet and exercise.

Part of the problem lies in the idea that exercise allows for another helping at dinner or a snack in front of the TV. And it doesn’t help that the average gym rat thinks he works long and hard enough to warrant a post workout snack. This is especially true if the food consumed is considered “healthy.”

Take chocolate milk for example. Touted as the perfect post-workout snack, it’s not unusual to see exercisers gulp down a carton after a workout. But at 400 calories per 500 mL carton, the average exerciser would have to have spent more than 60 minutes walking or 30-plus minutes running to match the calories consumed post exercise.

It’s exactly this kind of math that led Ottawa weight loss specialist Yoni Freedhoff, medical director at the Bariatric Medical Institute in Ottawa and author of The Diet Fix: Why Diets Fail and How to Make Yours Work, to suggest that it’s almost impossible to outrun your fork.

“Eighty per cent of weight is from dietary choice and 20 per cent from fitness,” Freedhoff said.

Following up on the Ottawa University study, a research team out of the U.K. decided to see whether the findings would hold when study subjects worked out a little harder and a little longer.

Suggesting that a 200-300 calorie workout would be easily matched at the buffet table (a bagel with cream cheese is anywhere from 250-350 calories depending on the size of the bagel and the amount of cream cheese), the U.K. study used bouts of exercise that reached 60 and 90 per cent of VO2 max (maximum aerobic power) compared to the 50 per cent of VO2 max of the Ottawa study. Subjects maintained that intensity until they burned 450 calories while running on the treadmill. They then followed the same post workout protocol, showering and heading to the buffet table after their workout with the following instructions: “Consider the exercise bout that you have just completed and the amount of energy that you expended, or the number of calories that you burned. Now, try to match that energy, or number of calories in the food that you consume from the buffet.”

Unlike the Ottawa study, the subjects underestimated the calories burned during the moderate intensity workout (298 calories compared to the 450 they burned) but were pretty close when it came to estimating their energy output during the higher intensity workout. But, what’s really interesting is that they overate to the same extent regardless of the intensity of the workout (20 per cent after the moderate intensity workout and 22 per cent after the high intensity workout).

Again, keep in mind that the difference in calories consumed over those burned was based on the number of calories they thought they expended — not on the number of calories they burned. That’s an important distinction because it’s the fact that most of us struggle with estimating how many calories we expend and how many we consume that is being validated.

Also worth noting: even when study subjects were specifically tasked with matching the number of calories burned with those consumed, they were unable to get it right.

The lesson for all of us is that the move more and eat less philosophy of weight loss isn’t as simple as it seems, especially considering that the calories burned in a typical 30-minute workout are replaced in mere seconds by even the healthiest of smoothies.

Keep this in mind the next time you reach for your post exercise snack or the extra helping at lunch that you “earned” after a tough early morning workout. While there’s no argument about the value of exercise when it comes to maintaining health and contributing to weight loss, it’s not a strong player when used solely to get rid of that spare tire.

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‘Move more eat less’ isn’t as simple as it seems, University of Ottawa study shows